Allergies are a major health problem in the United States, reducing quality and life and resulting in significant health care costs. Ocular allergies affect as many as one in five people in the United States. Improved and novel treatments are clearly needed for allergic diseases. Mast cells play a critical role in ocular allergy, but the exact molecular mechanisms driving mast cell activation are poorly understood. Molecules that are necessary for ocular hypersensitivity reactions - and that might be suitable targets for treatments of ocular allergy - include the chemokines eotaxin-1 and MIP-1, their respective receptors CCR3 and CCR1, and molecules regulated by these signals. The goal of the study outlined below is to better define the roles of these molecules in ocular allergy. The study contains the following specific aims: 1) to examine the mast cell-priming role of eotaxin-1-CCR3 activity in a murine model of allergic conjunctivitis; 2) to explore the costimulatory role of MIP-1-CCR1 signaling in mast cell activation in vivo; 3) to identify proteins that mediate the mast cell effects of MIP-1-IgE costimulation in vivo; and 4) to identify gene products that, when upregulated, mediate the mast cell effects of MIP-1-IgE costimulation in vivo. The adoptive transfer model for assessing in vivo mast cell activity will be used as a component of all four aims. In this model, mast cells with a genotype of interest are injected into mast cell-deficient mice, which have a defective ocular allergy response. Reconstituted mast cell populations lacking critical genes will fail to restore early-phase and/or late-phase responses to ocular allergens. For the first two aims, mast cells deficient for eotaxin-1, MIP-1, CCR1 or CCR3 will be used for in vitro assays of mast cell differentiation and function, and for the in vivo adoptive transfer model. For the third aim, the roles of potential proteomic mediators of MIP-1-CCR1 activity, specifically vimentin and PI3K, will be assessed using the in vitro mast cell assays and in vivo adoptive transfer model. For the fourth aim, the roles of transcriptionally upregulated mediators of MIP-1-CCR1 activity, specifically CCL7 and RGS1, will be assessed using the in vitro mast cell assays and in vivo adoptive transfer model. The results of these studies will provide a better understanding of the roles of chemokine signaling in mast cell function and ocular allergy, and may identify novel targets for therapeutic strategies.